This invention relates to internetworking architectures, such as multi-protocol over ATM (MPOA) and, more particularly, to a distributed router system having multiple routing and forwarding components with a configuration server to map the forwarding components to the routing components.
The ATM Forum""s multi-protocol over ATM (MPOA) introduces the concept of internetworking service features between local area networks over an asynchronous transfer mode (ATM) backbone. This internetworking service relies on local area network emulation (LANE) principles to establish and control connectivity. Co-pending U.S. application Ser. No. 08/676,256, filed Sep. 16, 1996 and assigned to the assignee of the present application, provides greater detail respecting the implementation of an MPOA type switch system.
A more recent development relating to MPOA is Newbridge Network Corporation""s internetworking (CSI) solution which provides internetworking service to multiple sub-networks by introducing the concept of Realms. CSI embodies a non-broadcast multi-access (NBMA) network based platform on which multiple and different types of internetworking servers are provided. An NBMA network is a form of virtual connection oriented backbone network, examples of which are ATM and Frame-Relay networks.
Examples of internetworking services include virtual private network (VPN) service and public Internet service. In CSI, a Realm is defined by a specific instance of an Internet or VPN service. Canadian patent application serial no. 2,217,275 (Agent""s docket no. 94218), filed on Oct. 3, 1997 and assigned to the assignee of the present application, provides greater detail with respect to the CSI system.
Distributed routers, as implemented in MPOA and CSI, separate the forwarding component from the routing decision. In the aforementioned CSI system, the entity serving as the forwarding component is a forwarder and the entity making the routing decision is known as a route server.
Route servers provide an essential part of switched routing in the CSI system: route calculation and route distribution. A route server performs the complex routing computations and downloads simple forwarding tables derived therefrom to the forwarders The route servers run all the required internal and external routing protocols in the CSI system to provide both default connectivity and short-cut connections.
Edge forwarders are a particular type of forwarder employed in CSI. An edge forwarder is the logic component of the CSI system that performs the layer 3 edge forwarding functions, examples of which are the internetworking services card (ISC) for Newbridge""s 3617 Multi-services switch and Ridge forwarding engines. Together with the route servers, the edge forwarders provide routing services for host and customer devices connected to the CSI system.
The edge forwarders are configured statically with route server addresses to which they communicate for functionality. Such static address mapping thus requires reconfiguration whenever a route server""s point of attachment to the network is changed either manually or due to redundancy switchover.
It is an object of the present invention to satisfy the above limitation by introducing a configuration server which is responsible for mapping forwarders to route servers.
Therefore, in accordance with a first aspect of the present invention there is provided in a communications network for providing internetworking service function over an NBMA network a distributed routing system comprising: a plurality of routing means to generate and download forwarding tables respecting traffic through the networks; a plurality of forwarding means to implement forwarding functions according to the forwarding tables; and configuration means to dynamically configure interactivity between the routing means and the forwarding means.